Hot date or a particularly entertaining business meeting? Last week, Lainey Gossip spied Michelle Williams and Jason Segel chatting and laughing into the wee hours at the Chateau Marmont in Los Angeles, leading to speculation that a romance may be blossoming.

The night began as a threesome, with Michelle's joined-at-the-hip BFF Busy Philipps tagging along. But she ducked out early, leaving Williams and Segel alone.

For the next few hours, the funnyman reportedly made the Oscar-nominated actress laugh "a lot" as they enjoyed "several" glasses of wine.

Word is, the pair were "relaxed and happy" before making their exit (he paid the bill) around 1:30 a.m.

More chuckles are said to have ensued when Williams indicated that it was getting late, prompting Segel, who evidently lives near the hotel, to insist the night was still young.

Further fueling the romance rumors was Jason's left-field tweet on Sunday: "Honestly a totally hypothetical question but I'm curious. If I fell in love would you guys be happy?"

Judging from the overwhelmingly positive response to the possibility of the serious-seeming actress dating a guy who's willing to go naked on-screen for a laugh, "you guys" would be very happy indeed.

Since splitting with Heath Ledger a few months before his death in January 2008, Michelle, 31, has dated director Spike Jonze and been linked to filmmaker Cary Fukunaga. But she's mainly devoted herself to raising daughter Matilda, who, at 6, remains the spitting image of her late father.

"Relationships have always seemed very mysterious, and therefore worth exploring," she told Vogue in September. "I'm single, so it's still kind of a mystery -- a worthwhile mystery, one that I want to be on the scent of."

Segel, 32, who counts his "Freaks and Geeks" co-star Linda Cardellini among his exes, is no stranger to entertaining lovely ladies at the Chateau Marmont. Turns out the "Muppets" writer and star shared an almost identical evening with Rashida Jones a few years back, right down to the laughter and tab-paying.

So, tell us: Do you think Michelle and Jason would make a good couple? Weigh in below ...